1. Field of the Invention
The present invention is directed to detection systems operatively coupled to safety control systems for process machines, and in particular, to detection systems operatively coupled to safety control systems for manually fed process machines having at least one pinch point that can cause serious bodily injury to a worker caught in such a pinch point.
2. Background of the Invention
Process equipment safety systems are well known in the prior art. Most notably, prior art safety systems for industrial machines utilize infrared light curtains or some other sort of light beam safety system. The light curtains are positioned to encircle the machine or, if the machine is rigidly protected on other sides, a light curtain is positioned approximate the area of the unprotected portion of the machine. More often than not, the light curtain is placed in positions where workers have to interact with the machines.
An exemplary infrared curtain safety system comprises a series of infrared transmitters placed opposite a series of infrared detectors and aligned so that during operation of the safety curtain the infrared transmitters transmit infrared light directly to the infrared detectors. Thus, when activated, the transmitters transmit a beam of infrared light that is received by aligned detectors. When an object passes through the curtain, their corresponding detectors are no longer continuously detecting one or more beams of infrared light. This results in the safety system determining that someone or something has entered the work area of the machine. Several safety system responses are taught in the prior art. These responses include signals being sent to the controller of the machine to stop all motion of the machine or reverse the immediate motion of the machine.
An example of such an interaction between a worker and a machine may be shown by way of a worker placing a piece of material in a stretch bender. After the piece is positioned on the stretch bender, the worker removes his body and any other materials hazardous to the operation of the stretch bender and finally activates the light curtain. Generally, a signal from the light curtain that all the detectors are in fact receiving infrared light from the transmitters is required before the stretch bender initiates its process. If the safety curtain for any reason indicates that a corresponding detector is not receiving one or more infrared or other light beams, the safety system considers startup of the stretch bender to be hazardous. Only after the obstructions from the light beams have been removed is the stretch bender authorized to begin its task.
Other prior art safety systems have utilized infrared curtains in addition to other safety devices to provide a safety barrier around process machines. Most notably, prior safety systems have utilized one or more buttons that are depressed by a worker approximate the machine so that the worker and the worker's appendages are outside of the working zone of the machine. If one or more of these buttons fails to be depressed, an interrupt signal or some other corrective signals are sent to machine control unit to cease the movement of the machine and/or immediately reverse the previous movement of the machine. In addition, some prior art systems have utilized ultrasonic detection systems in addition to light curtains such that once the light curtain is pierced an interrupt signal to the machine is not automatic. The ultrasonic detector determines how close in proximity to the machine the object is that pierced the light curtain. If the object is dangerously close to the machine as determined by the ultrasonic detector, then an interrupt signal or other corrective action signal is sent to the machine.
Finally, some additional safety systems have utilized infrared detectors that detect the placement of a human hand. The systems utilize infrared transmitters that transmit infrared light and bounce the infrared light off of the human hand where it is detected by one or more detectors. If the human hand is not completely stagnant for the requisite period of time approximate a safe location as designated by the particular device, the infrared beams of light will not be reflected in sufficient amount or direction to be detected by the infrared detectors. Thus, the safety system determines that the workers appendages may potentially be within the operating zone of the machine. This being the determination, if the machine has not already started up, it will not start up; and, if it has already started its process, it will cease continuation of that process.